Monoalkyl tin trialkoxides and/or monoalkyl tin triamides with particulate contamination and corresponding methods

ABSTRACT

The purification of monoalkyl tin trialkoxides and monoalkyl tin triamides are described using fractional distillation and/or ultrafiltration. The purified compositions are useful as radiation sensitive patterning compositions or precursors thereof. The fractional distillation process has been found to be effective for the removal of metal impurities down to very low levels. The ultrafiltration processes have been found to be effective at removal of fine particulates. Commercially practical processing techniques are described.

FIELD OF THE INVENTION

The invention relates to monoalkyl tin compositions, specificallymonoalkyl tin trialkoxides and monoalkyl tin triamides, that have beenprocessed to have low metal contamination and/or low particlecontamination. The invention further relates to solutions made with thelow metal contamination monoalkyl tin compositions that can be used forradiation patterning, such as photoresists effective for EUVlithography. The invention further relates to corresponding processesfor forming the purified monoalkyl tin compositions.

BACKGROUND OF THE INVENTION

Solutions of organometallic compounds form coatings containing radiationsensitive metal-carbon bonds that can be used to pattern structureslithographically. The processing of semiconductor materials and deviceswith ever shrinking dimensions results in demands for high-puritysolutions with low particle counts to mitigate contamination issues,minimize pattern defects, and enable the advantages of organometallicphotoresists. The processing and performance of semiconductor materialsfor microelectronics applications can be sensitive to metalcontaminants. To produce microelectronic products using lithography, theproper control of metal contaminants can reduce waste from failure tomeet product specifications.

SUMMARY OF THE INVENTION

In a first aspect, the invention pertains to a composition comprising asolvent and a monoalkyl tin trialkoxide (RSn(OR′)₃) having a tinconcentration from about 0.004M to about 1.4 M and a contamination withother metals or metalloid elements of each no more than 10parts-per-billion (ppb) by mass.

In a further aspect, the invention pertains to a composition comprisinga solvent and a monoalkyl tin triamide (RSn(NR′₂)₃) having a tinconcentration from about 0.01M to about 1.4M and a contamination withother metals or metalloid elements of each no more than 50parts-per-billion (ppb) by mass.

In another aspect, the invention pertains to a method of forming amonoalkyl tin trialkoxide or monoalkyl tin triamide having low metalcontamination, in which the method comprises performing fractionaldistillation of a monoalkyl tin trialkoxide or monoalkyl tin triamidewith temperatures, pressures and equipment selected to collect themonoalkyl tin trialkoxide or monoalkyl tin triamide with a contaminationof other metals or metalloids of each not more than 50 ppb by mass. Insome embodiments, the composition for purification is placed in adistillation vessel (and up to 10 vol % tris(2-aminoethyl)amine with themonoalkyl tin triamide) in association with a heating element andwherein at least about 0.5 vol % is left in the distillation vessel.

In other aspects, the invention pertains to a composition comprising asolvent and monoalkyl tin trialkoxide (RSn(OR′)₃) or monoalkyl tintriamide (RSn(NR′₂)₃) with a tin concentration from about 0.005M toabout 0.5M and having no more than about 40 particles per mL with aparticle size of at least about 70 nm.

Moreover, the invention pertains to a method for preparing a radiationsensitive composition comprising solvent and an organometalliccomposition selected from the group consisting of monoalkyl tintrialkoxide, monoalkyl tin triamide, or a mixture thereof, the methodcomprising the step of flowing the composition using an impeller stylepump through a filter to remove particulate contaminants to form afiltered composition with a measured concentration of particles with asize of at least 70 nm is below 100 particles per mL.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a fractional distillation apparatussuitable for purification of monoalkyl tin compositions.

FIG. 2 is a schematic view of a filtration apparatus suitable forremoval of fine particulates from monoalkyl tin compositions.

FIG. 3 is a ¹¹⁹Sn NMR spectrum of a t-BuSn(NMe₂)₃ sample as synthesized,where t-Bu represents a tertiary butyl ligand and NMe₂ represents adimethylamide ligand.

FIG. 4 is a ¹¹⁹Sn NMR spectrum of the t-BuSn(NMe₂)₃ sample used toobtain the spectrum of FIG. 3 following purification by fractionaldistillation.

FIG. 5 is a ¹¹⁹Sn NMR spectrum of a t-BuSn(OtAm)₃ sample followingpurification by fractional distillation, where t-Bu represents atertiary butyl ligand and OtAm represents a tertiary amyl ligand.

FIG. 6 is a schematic view of a specific exemplified filtration system.

DETAILED DESCRIPTION OF THE INVENTION

Monoalkyl tin alkoxides and monoalkyl tin amides have been formed havingvery low metal contamination in the parts per billion range. The tincompositions can be selected to have high EUV absorption such that thecompositions can be useful for EUV patterning in semiconductormanufacturing. In particular, monoalkyl tin compositions have been foundto provide very effective EUV patterning resists that can be used toform very fine structures. Fractional distillation has been found to beeffective for the purification of the compounds with respect to metalimpurities. The processing can also be used to separate the monoalkyltin compounds from polyalkyl tin contaminants. The purified compositionscan then be further diluted with semiconductor grade solvents, andoptionally others compositions, to form desired patterning products.Additionally or alternatively, improved filtering techniques can alsoprovide low particulate contamination in radiation resist compositions.The purified radiation resist compositions are suitable for patterningof very small features with low patterned product failure rates and highyield.

For semiconductor processing and other microelectronics applications,metal contaminants can be detrimental and can result in product failureand high processing loss rates due to failure of components to meetspecifications. The threshold contaminant levels that are detrimentalfor significant products can be very low. Therefore, there isconsiderable motivation to reduce significantly metal contaminants.Radiation based patterning has been the key process technology to formever shrinking component sizes, and the demand for this shrinkage haspushed radiation based patterning into higher energy radiation regimes,such as extreme ultra violet light and electron beams. To take advantageof the finer patterns available using higher energy radiation,organometallic based radiation resists, especially organotin compounds,have been found with a high level of performance. For processing withorganotin compounds, in addition to managing the introduction andremoval of the tin, it is desirable to avoid introduction ofcontamination by other metals. As described herein, contaminating metalscan be reduced to parts-per-billion by mass levels.

It has been discovered that appropriate purification processing can beused to effectively reduce non-tin metal contamination to very lowlevels specifically for monoalkyl tin trialkoxides and monoalkyl tintriamides. Based on experience with the application of thesecompositions for radiation resist materials, it can also be desirable toeliminate polyalkyl tin compounds, and the processing for the metalcontaminations can also be effective to remove the polyalkyl tincontaminants. In particular, the monoalkyl tin trialkoxides andmonoalkyl tin triamides can be purified using fractional distillationusing a suitable distillation column and in some embodiments throughappropriate selection of the distillation fractions. Correspondinghandling of the purified compositions can maintain the high purity ofthe compositions. Furthermore, the purified compositions can be filteredto remove particulate contaminants that can result in patterningimperfections. Improved filtration can use continuous impeller stylepumps to circulate and recirculate the photoresists throughsemiconductor grade filters to remove particulates. The particulateremoval can be verified using in line light scattering measurements.

The use of organometallic tin compositions as photoresists, especiallyfor extreme ultraviolet based patterning, is generally based onmonoalkyl tin oxo hydroxo compounds. The oxo hydroxo compounds can bemade in solution, or they can be made during and/or subsequent to an insitu coating process involving water based hydrolysis of RSnX₃ compoundsin which R is an alkyl group and Sn—X is a hydrolysable group. Monoalkyltin triamides and monoalkyl tin trialkoxides are suitable precursorcompounds for forming the monoalkyl tin oxo hydroxo compounds, andmonoalkyl tin triamides are suitable precursors for forming monoalkyltin trialkoxides. Current best practices for using these resistcompositions comprise forming a coating of monoalkyl tin trialkoxide,and hydrolyzing the trialkoxide in situ to form the oxo hydroxocompositions with a volatile alcohol by product that readily evaporates.The processing and compositions described herein are generally usefulfor such previously described processes and compositions as well as forother monoalkyl tin based photoresist patterning processes andcompositions beyond the current best practices. Monoalkyl tin triamidescan thus be useful intermediate products in the preparation of organotinphotoresists either through their use to synthesize monoalkyl tintrialkoxides or for the deposition and in situ processing to form themonoalkyl tin oxo-hydroxo compositions.

Methods for the preparation of monoalkyl tin triamides have previouslyemployed lithium reagents to convert tin tetraamides to the desiredtriamides. For example, t-butyl tris(diethylamido)tin, (t-BuSn(NEt₂)₃),can be synthesized with a lithium reagent according to the method ofHänssgen, D.; Puff, H.; Beckerman, N. J. Organomet. Chem. 1985, 293,191, incorporated herein by reference. These methods with lithiumreagents, however, can produce a mixture of monoalkyl and dialkyl tinproducts. Lithium alkyls are often highly reactive compounds. They canignite spontaneously with air, moisture, or both to form flammablealkanes and corrosive lithium hydroxide. Consequently, great care andexpense are required to handle lithium alkyls. Also, lithiumcontaminants can be undesirable for semiconductor applications, and theprocesses described herein are directed to reduction of non-tin metalcontaminants. While the lithium contamination can be removed usingpurification techniques described herein, improved synthesis techniqueshave been developed that do not use the lithium reactants. Theseimproved synthesis techniques are described in co-pending U.S. patentapplication Ser. No. 15/950,292 to Edson et al. (hereinafter the '292application), entitled “Monoalkyl Tin Compounds With Low PolyalkylContamination, Their Compositions and Methods,” incorporated herein byreference. Further processing can be used to decrease both the polyalkyltin contaminants and the non-tin metal contaminants.

The use of alkyl metal coordination compounds in high performanceradiation-based patterning compositions is described, for example, inU.S. Pat. No. 9,310,684 to Meyers et al., entitled “OrganometallicSolution Based High Resolution Patterning Compositions,” incorporatedherein by reference. Refinements of these organometallic compositionsfor patterning are described in published U.S. patent applications2016/0116839 A1 to Meyers et al., entitled “Organometallic SolutionBased High Resolution Patterning Compositions and CorrespondingMethods,” and 2017/0102612 A1 to Meyers et al. (hereinafter the '612application), entitled “Organotin Oxide Hydroxide PatterningCompositions, Precursors, and Patterning,” both of which areincorporated herein by reference.

The compositions synthesized herein can be effective precursors forforming the alkyl tin oxo-hydroxo compositions that are advantageous forhigh resolution patterning. The alkyl tin precursor compositionscomprise a group that can be hydrolyzed with water or other suitablereagent under appropriate conditions to form the alkyl tin oxo-hydroxopatterning compositions, which can be represented by the formulaRSnO_((1.5-(x/2)))(OH)_(x) where 0<x≤3. The hydrolysis and condensationreactions that can transform the compositions with hydrolyzable Sn—Xgroups are indicated in the following reactions:

RSnX₃+3 H₂O→RSn(OH)₃+3 HX,

RSn(OH)₃→RSnO_((1.5-(x/2)))OH_(x)+(x/2)H₂O.

If the hydrolysis product HX is sufficiently volatile, in situhydrolysis can be performed with water vapor during the substratecoating process, but the hydrolysis reaction can also be performed insolution to form the alkyl tin oxo-hydroxo compositions. Theseprocessing options are described further in the '612 application.

The monoalkyl tin triamide compositions generally can be represented bythe formula RSn(NR′)₃, where R and R′ are independently an alkyl or acycloalkyl with 1-31 carbon atoms with one or more carbon atomsoptionally substituted with one of more heteroatom functional groupscontaining O, N, Si, Ge, Sn, Te, and/or halogen atoms or an alkyl or acycloalkyl further functionalized with a phenyl or cyano group. In someembodiments, R′ can comprise ≤10 carbon atoms and can be, for example,methyl, ethyl, propyl, isopropyl, butyl, t-butyl, isobutyl, or t-amyl.The R group can be a linear, branched, (i.e., secondary or tertiary atthe metal-bonded carbon atom), or cyclic hydrocarbyl group. Each R groupindividually and generally has from 1 to 31 carbon atoms with 3 to 31carbon atoms for the group with a secondary-bonded carbon atom and 4 to31 carbon atoms for the group with a tertiary-bonded carbon atom. Inparticular, branched alkyl ligands can be desirable for some patterningcompositions where the compound can be represented as R¹R²R³CSn(NR′)₃,where R¹ and R² are independently an alkyl group with 1-10 carbon atoms,and R³ is hydrogen or an alkyl group with 1-10 carbon atoms. As notedbelow, this representation of alkyl ligand R is similarly applicable tothe other embodiments generally with R¹R²R³CSn(X)₃, with X correspondingto the trialkoxide or triamide moieties. In some embodiments R¹ and R²can form a cyclic alkyl moiety, and R³ may also join the other groups ina cyclic moiety. Suitable branched alkyl ligands can be, for example,isopropyl (R¹ and R² are methyl and R³ is hydrogen), tert-butyl (R¹, R²and R³ are methyl), tert-amyl (R¹ and R² are methyl and R³ is —CH₂CH₃),sec-butyl (R¹ is methyl, R² is —CH₂CH₃, and R³ is hydrogen), neopentyl(R¹ and R² are hydrogen, and R³ is —C(CH₃)₃), cyclohexyl, cyclopentyl,cyclobutyl, and cyclopropyl. Examples of suitable cyclic groups include,for example, 1-adamantyl (—C(CH₂)₃(CH)₃(CH₂)₃ or tricyclo(3.3.1.13,7)decane bonded to the metal at a tertiary carbon) and 2-adamantyl(—CH(CH)₂(CH₂)₄(CH)₂(CH₂) or tricyclo(3.3.1.13,7) decane bonded to themetal at a secondary carbon). In other embodiments hydrocarbyl groupsmay include aryl or alkenyl groups, for example, benzyl or allyl, oralkynyl groups. In other embodiments the hydrocarbyl ligand R mayinclude any group consisting solely of C and H and containing 1-31carbon atoms. In summary, some examples of suitable alkyl groups bondedto tin include, for example, linear or branched alkyl (i-Pr ((CH₃)₂CH—),t-Bu ((CH₃)₃C—), Me (CH₃—), n-Bu (CH₃CH₂CH₂CH₂—)), cyclo-alkyl(cyclo-propyl, cyclo-butyl, cyclo-pentyl), olefinic (alkenyl, aryl,allylic), or alkynyl groups, or combinations thereof. In furtherembodiments suitable R groups may include hydrocarbyl groups substitutedwith hetero-atom functional groups including cyano, thio, silyl, ether,keto, ester, or halogenated groups or combinations thereof.

The alkyl tin trialkoxide compositions can be represented by theformula)RSn(OR⁰)₃. The alkyl tin trialkoxide can be synthesized fromalkyl tin triamide, although other synthesis pathways can be used, suchas those described in the '292 application wherein synthesis ofmonoalkyl tin trialkoxides is achieved from alkyl triamido tincompositions. The alkyl triamido tin compositions can be represented bythe formula RSn(NR″COR″′)₃. The R groups in the formulas for the alkyltin trialkoxide and alkyl triamido tin compositions can be the same Rgroups as summarized above for the alkyl tin triamide compositions, andthe corresponding discussion of these R groups above is as if copied inthis paragraph in its entirety. The monoalkyl triamido tin compositionsare not discussed further herein. For the alkoxide ligands —OR⁰, the R⁰groups can be independently hydrocarbon groups with 1-10 carbon atoms,such as methyl groups, ethyl groups, or the like.

Polyalkyl tin impurity compositions may affect condensation of thecoated resist material and contribute to radiation resist outgassingduring lithographic processing, which increases the potential for tincontamination of equipment used for film deposition and patterning.Based on these concerns, a significant desire exists to reduce oreliminate the dialkyl or other polyalkyl components of resistcompositions. The monoalkyl tin trialkoxide compositions can bedesirable constituents in precursor patterning composition solutionssince they are amenable to in situ hydrolysis and condensation to formmonoalkyl tin oxo-hydroxo compositions with alcohol byproducts that aregenerally and appropriately volatile for removal commensurate with insitu hydrolysis. As described herein, contaminants from polyalkyl tincompounds are removed in a distillation of a monoalkyl tin triamidecompositions, although direct purification of the monoalkyl tintrialkoxide compositions may be suitable to remove polyalkylcontaminants.

Monoalkyl tin triamide compositions can be directly synthesized withrelatively low polyalkyl contaminants using any one of three methodssummarized herein, and these methods are described in more detail in the'292 application. The purified monoalkyl tin triamides and the monoalkyltin trialkoxides can have both low polyalkyl contamination and lownon-tin metal contamination. Due to particularly effective purificationof the monoalkyl tin trialkoxides relative to compounds with non-tinmetals, the trialkoxides can be purified to very low metalcontamination, as demonstrated in the Examples below. With respect tothe polyalkyl tin contaminants, these trace metal concentrations can bereduced to undetectable levels.

The fractional distillation processes described herein can be effectiveto remove non-tin metal contaminants to a significant degree formonoalkyl tin triamides and in particular for monoalkyl tintrialkoxides. Generally, the monoalkyl tin composition is diluted in anorganic solvent for further processing, and these diluted solutions aresuitable for analysis with ICP-MS or ICP-AES techniques, as describedfurther below, to obtain the metal concentrations down to low levels.The evaluation of the metal contamination as well as the formation ofresist precursor formulations generally involves dilution with anorganic solvent. With respect to evaluation of the metal contamination,the pure compositions are diluted to prevent saturation of the massspectrometer detector by the high tin concentration. Suitable solventscan be used that do not contribute themselves to significant metalcontaminants.

Monoalkyl tin triamides can be purified and dissolved in solvents toreduce each non-tin metal element to levels of no more than about 50parts-per-billion (ppb) by mass, in further embodiments no more thanabout 40 ppb, in other embodiments no more than about 30 ppb, and inadditional embodiments no more than about 25 ppb by mass. Solutions ofmonoalkyl tin trialkoxides can be purified to reduce each non-tin metalelement to particularly low levels of no more than about 3 ppb, infurther embodiments no more than about 2 ppb, and in other embodimentsno more than about 1.5 ppb by mass. As seen in the examples below, themetal contaminant levels generally can be reduced for most non-tinmetals to below the detection limit, generally less than 1 ppb. For themonoalkyl tin trialkoxide exemplified below, of 23 non-tin elements,only barium was measured slightly above the detection limit, while stillbeing below 1 ppb. A person of ordinary skill in the art will recognizethat additional ranges of non-tin metal purification within the explicitranges above are contemplated and are within the present disclosure.

The resist precursor composition can be conveniently specified based ontin ion molar concentration. The resist precursor compositions can havethe values of low non-tin metal contamination as specified in theprevious paragraph. In general, the resist precursor solution generallycomprises from about 0.0025 M to about 1.4 M tin cation, in someembodiments from about 0.004M to about 1M, in further embodiments fromabout 0.005 M to about 0.75 M, also in some embodiments from about 0.01Mto about 1M, and in additional embodiments from about 0.01 M to about0.5 M tin cation. A person of ordinary skill in the art will recognizethat additional concentration ranges and values within the explicitranges above are contemplated and are within the present disclosure.

The non-tin metal contaminants can be evaluated using standardanalytical techniques, in particular inductively coupled plasma-massspectrometry (ICP-MS) and/or inductively coupled plasma-atomic emissionspectrometry (ICP-AES). These techniques can measure metals to very lowlevels. As indicated in the Examples, measurements were made at acommercial analytical testing facility. For handling the samples andintroduction of the samples into the analytical equipment, the samplesare diluted with solvent. Suitable solvents are described below for theformation of resist precursor coating solutions, and in the examples,4-methyl-2-pentanol was used as the solvent. Semiconductor gradesolvents with metal contamination levels in the parts per trillion arecommercially available from Alfa Aesar, Fuji Film, KMG Chemicals (TX,USA), TOK America, Inc., Honeywell Electronic Materials, and othersuppliers. Proper handling of the solutions and storage containers anddilution of the monoalkyl tin composition with a suitable semiconductorgrade solvent having metal contamination in the parts per trillion rangeshould not alter the measurement of the non-tin metal contaminantsrelative to the tin over a broad concentration range.

Ultra-pure solvents are commonly stored and transported in plasticcontainers made of high-density polyethylene (HDPE),polytetrafluoroethylene (PTFE), or polypropylene (PP). AicelloCorporation CLEANBARRIER™ (CB) bottles are constructed from HDPE anddesigned to store and transport pure semiconductor grade chemicals withlow particle counts and low trace metal concentrations. Photoresists canalso be stored in dealkalized glass bottles. Commercial containers arecommonly made with soda-lime glass. This glass contains a highconcentration of sodium, which solvents and liquids can leach from theglass. A process of dealkalization depletes sodium from the surface of aglass container to eliminate sodium leaching.

Also, the monoalkyl tin compositions can be filtered to eliminateparticulate contaminants. An improved procedure for performing thefiltering is described in detail below. The filtering and evaluation ofthe filtered composition is performed with a sample dissolved insolvent. The dilution is generally performed to the concentrations ofthe resist composition since the desired resist composition is filtereddirectly and then loaded into a container for storage and transport. Tinconcentrations in resist precursor compositions are presented above.

The particulate contamination can be measured using particle measuringequipment. For example, for photoresists generally, Rion Corporation(Japan) sells particle counters based on light scattering, and such aparticle counter is used in the Examples below. An appropriatelyselected particle counter can perform in line particle measurement bysampling a solution from a filtration flow system. The results from theparticle measurements are presented in number of particles permilliliter (mL) of fluid. The particular particle counter would haveselected ranges of particle size that are measured, and the results inthe Examples below provide particle counts at sizes of 70 nm or larger.

The removal of particulates from organometallic photoresists isdescribed in published PCT application WO 2017/163922 to Tsubaki et al.(hereinafter Tsubaki application), entitled (translated) “ActiveRay-Sensitive or Radiation-Sensitive Composition, Method for PurifyingActive Ray-Sensitive or Radiation-Sensitive Composition, Pattern-FormingMethod, and Method for Producing Electronic Device,” incorporated hereinby reference. The filtering methods in the Tsubaki application weredirected to various metal compounds with selected ligands, andexemplified butyl tin oxide hydroxide (C₄H₉—SnOOH) in Example 9. Tsubakidoes not discuss filtering alkyl metal alkoxides. As described below,the filtration of alkyl metal alkoxides to remove particulates presentsparticular challenges.

Based on the filtration processes developed and described herein, resistcompositions comprising monoalkyl metal trialkoxides and/or monoalkyltin triamides in an organic solvent at a concentration from about0.0025M to about 1.4 M and in some embodiments from about 0.01M to about0.5 M (based on moles tin) can be purified to remove particulates suchthat the solutions have no more than about 3 particles per mL withaverage sizes greater than 150 nm, in further embodiments no more thanabout 2 particles/mL, and in additional embodiments no more than about 1particle/mL with average sizes greater than 150 nm as determined bylight scattering. Using commercially available particle counters, suchas a Rion KS-41B Liquid-Borne Particle Sensor with optionalcapabilities, particles can be counted down to 70 nm using lightscattering. Using filtration techniques herein, alkyl metal alkoxides inorganic solvents with concentrations from 0.025M to 1.4M and in someembodiments from about 0.05M to about 0.5 M (based on moles tin) can bepurified to have particle contaminants of no more than 25 particles/mLfor particle sizes between 70 nm and 150 nm, in further embodiments nomore than 20 particles/mL, and in additional embodiments no more than 12particles/mL. A person of ordinary skill in the art will recognize thatadditional ranges of particle contamination within the explicit rangesabove are contemplated and are within the present disclosure. Thesecompositions can be purified also with respect to lowering metalcontamination and polyalkyl metal contaminants using the processingdescribed herein to produce resist compositions simultaneously with lowmetal contamination, low polyalkyl metal contamination, and lowparticulate contamination, especially monoalkyl tin trialkoxidecompositions.

In general, the synthesis processes for preparing monoalkyl tintriamides comprise reacting a compound having an alkyl donating group,also described as an alkylating agent, with a tin tetraamide. Desirableresults have been achieved in which the alkylating agent may be aGrignard reagent, a diorganozinc reagent, or a mono-organozinc amide.These syntheses can directly produce the monoalkyl tin triamides withlow polyalkyl contaminants that can be used for forming resists or thatcan be additionally purified to reduce the polyalkyl contaminant levelseven further. The methods with Zn reagents were specifically developedfor synthesis of pure monoalkyl tin triamides containing secondary alkylgroups. In the synthesis methods, the alkylating agent selectivelyreplaces an amide group of tin tetraamide with the alkyl group withimproved selectivity and yield of monoalkyl tin triamides. Thus, in someembodiments, the reaction selectively produces monoalkyl tin triamidewith low polyalkyl tin contaminants, particularly low dialkyl tincontaminants. The methods are especially useful for branched alkylsystems. The monoalkyl tin triamides with low polyalkyl contaminants canthen be used to form monoalkyl tin trialkoxides with low polyalkylcontaminants.

For the reactions to form the monoalkyl tin triamide compounds, the tintetraamide compounds can be obtained commercially or synthesized usingknown techniques. For example, tetrakis(dimethylamido)tin, Sn(NMe₂)₄, isavailable from Sigma-Aldrich. For the synthesis of the monoalkyl tincompositions, the tin tetraamide reactant in solution generally can havea concentration of between about 0.025 M and about 1.5 M, in furtherembodiments between about 0.05 M and about 1 M, or in additionalembodiments between about 0.1 M and 0.75 M. A person of ordinary skillin the art will recognize that additional ranges of reactantconcentrations within the explicit ranges above are contemplated and arewithin the present disclosure. In general, the relevant reactions tointroduce an alkyl ligand to Sn can be initiated with the tintetraamides in solution in a reactor under inert gas purge and in thedark. In alternative embodiments, some or all of the tin tetraamidereactant is added gradually, in which case the concentrations above maynot be directly relevant since higher concentrations in the graduallyadded solution may be appropriate and the concentrations in the reactormay be transient.

The alkylating agent generally is added in an amount relatively close toa stoichiometric amount. In other words, the alkylating agent is addedto provide the molar equivalent of one alkyl group for one tin atom. Ifan alkylating agent can provide multiple alkyl groups, such as thediorganozinc compounds that can donate two alkyl groups per zinc atom,then the stoichiometric amount of the alkylating agent is adjustedaccordingly to provide about one alkyl group for each Sn. So, fordiorganozinc compounds on the order of one mole of Zn is required pertwo moles of Sn. The amount of the alkylating agent can be about ±25%,about ±20%, or about ±15% relative to the stoichiometric amount of thereagent, or in other words the stoichiometric amount of the reagent + or− a selected amount to achieve desired process performance. A person ofordinary skill in the art will recognize that additional ranges ofrelative amount of alkylating agent within the explicit ranges above arecontemplated and are within the present disclosure.

The alkylating agent dissolved in organic solvent can be added graduallyto the reactor, such as dropwise or flowed at a suitable rate to controlthe reaction. The rate of addition can be adjusted to control thereaction process, such as over the course of time between about 1 minuteto about 2 hours and in further embodiments from about 10 minutes toabout 90 minutes. The concentration of alkylating agent in the additionsolution can be adjusted within reasonable values in view of the rate ofaddition. In principle, the alkylating reagent can start in the reactorwith the gradual addition of the tin tetraamide. A person of ordinaryskill in the art will recognize that additional ranges of alkylatingagents and additional times within the explicit ranges above arecontemplated and are within the scope of the present disclosure.

The reaction to introduce the alkyl ligand to the tin atom may beconducted in a low oxygen, substantially oxygen free, or an oxygen-freeenvironment, and an active inert gas purge can provide the appropriateatmosphere, such as an anhydrous nitrogen purge or an argon purge. Insome embodiments, an additive, such as a neutral coordinating base, canbe used during the reaction to hinder formation of undesired polyalkylspecies. The following additives have been observed to reduce additionof a second alkyl group to tin: pyridine, 2,6-lutidine, 2,4-lutidine,4-dimethylaminopyridine, 2-dimethylamino pyridine, triphenylphosphine,tributylphosphine, trimethylphosphine, 1,2-dimethoxyethane, 1,4-dioxane,and 1,3-dioxane. Other neutral coordinating bases may function in thesame way. The reaction can optionally further comprise from about 0.25to about 4 moles of neutral coordinating base per mole of tin. Thereaction can be shielded from light during the reaction. The reactionmay be conducted in an organic solvent, for example, an alkane (such aspentane or hexane), an aromatic hydrocarbon (such as toluene), ether(such as diethyl ether, C₂H₅OC₂H₅), or mixtures thereof. The solvent maybe anhydrous to avoid reaction with water. The reaction generally is runfor about 15 minutes to about 24 hours, in further embodiments fromabout 30 minutes to about 18 hours and in additional embodiments fromabout 45 minutes to about 15 hours. The temperature during the reactionmay be between about −100° C. and about 100° C., in further embodimentsbetween about −75° C. and about 75° C., and in additional embodimentsbetween about −60° C. and about 60° C. Cooling or heating can be used tocontrol the reaction temperature within the desired range, and controlof the rate of reactant addition can also be used to influencetemperature evolution during the course of reaction. The productmonoalkyl tin triamide generally is an oil that can be purified usingvacuum distillation, as discussed further below. Typical yields havebeen observed to be approximately 50 to 85 percent. A person of ordinaryskill in the art will recognize that additional ranges of concentrationsand process conditions within the explicit ranges above are contemplatedand are within the present disclosure.

In some embodiments, the alkylating agent can be a Grignard reagent, adiorganozinc reagent, or a mono-organozinc amide. A Grignard reagent canbe an organo-magnesium halide.

Specifically, a Grignard reagent in the described reaction may be RMgX,where X is a halide, generally Cl, Br, or I. Correspondingly, thediorganozinc reagent may be R₂Zn. In further embodiments the alkylatingagent is a mono-organozinc amide (RZnNR′2), where R′ is an alkyl orcycloalkyl group, which can be substituted with a hetero-atom, and insome embodiments, R′ may have between 1 and 8 carbon atoms. R may be analkyl or cycloalkyl and have between 1 and 31 carbon atoms, andgenerally R can be described more fully as above with respect to the Rmoiety of the product compositions, which is as if incorporated for thisdiscussion in its entirety. For example, the alkyl or cycloalkyl may bebranched, can comprise aromatic groups and/or may have one or moreheteroatom functional groups containing atoms such as O, N, Si, Ge, Sn,and/or a halogen. Grignard reagents are available commercially or can besynthesized using known methods. Commercial sources include AmericanElements Company, Sigma-Aldrich, and many other suppliers.

Diorganozinc compounds are available commercially or can be synthesizedusing known techniques. Commercial sources include, for example, AlfaAesar, Sigma-Aldrich, Rieke Metals (Nebraska, USA) and Triveni Chemicals(India). The mono-organozinc amides can be synthesized, for example,from an alkyl zinc halide (RZnX, X═I, Br, Cl) and lithium amide(LiNR′2), which are commercially available reagents from Sigma-Aldrich.

As noted above, the monoalkyl tin triamides can also be used tosynthesize corresponding monoalkyl tin trialkoxides, although themonoalkyl tin trialkoxides can be synthesized using other approaches. Inparticular, monoalkyl tin trialkoxides can be produced by reacting thecorresponding monoalkyl tin triamide with an alcohol in a non-aqueoussolvent containing a base. The low polyalkyl tin contaminants in themonoalkyl tin triamides using the processing described herein can becarried forward into the product monoalkyl tin trialkoxides, so that theproduct monoalkyl tin trialkoxides have low dialkyl tin contaminantsessentially at the mole percentages described above. Suitable organicsolvents include, for example, an alkane (such as pentane or hexane), anaromatic hydrocarbon (such as toluene), ether (such as diethyl ether,C₂H₅OC₂H₅), or mixtures thereof. The alcohol is selected to provide thedesired alkoxide group such that an alcohol ROH introduces the —OR groupas the ligand attached to tin. A list of suitable R groups is providedabove and correspondingly relate to the alcohol. Examples are providedbelow with t-amyl alcohol, but other alcohols can be similarly used toprovide the desired —OR alkoxide ligand.

For the reaction of the triamide to form monoalkyl tin trialkoxide, thealcohol can be provided roughly in a stoichiometric amount. Since thealcohol is used to replace three amide groups, three mole equivalents ofalcohol would be a stoichiometric amount. In general, the amount ofalcohol can be at least about −5% stoichiometric equivalents and infurther embodiments at least about a stoichiometric equivalent, and alarge excess of alcohol can be used. To facilitate purification of theproduct alkyl tin trialkoxide, a tetradentate coordination ligand orchelating agent can be added to coordinate with unreacted species toform complexes that do not vaporize during distillation. For example,tris(2-aminoethyl)amine (TREN), triethylenetetraamine (trien), or othertetradentate non-planar chelating agent can be used to complex with theunreacted species to facilitate purification. The chelating agent can beadded at a selected time from the start of the reaction to any timeprior to performing the distillation, in an amount from about 0.5 mole %to about 15 mole % and in further embodiments from about 1.0 mole % toabout 10 mole % relative to the tin molar quantity. A person of ordinaryskill in the art will recognize that additional ranges of reactantamounts within the explicit ranges above are contemplated and are withinthe present disclosure. If desired, a fractional distillation can beperformed to further purify the monoalkyl tin trialkoxides frompolyalkyl contaminants.

The monoalkyl tin triamides and the monoalkyl tin trialkoxides producedusing the methods described above or other methods not explicitlydescribed herein can be further purified using fractional distillation.It has been discovered that fractional distillation can be effective toreduce both metal contamination as well as contamination from other tincompounds, such as polyalkyl tin compounds. Thus, the product monoalkyltin compositions can be appropriately processed with fractionaldistillation to achieve valuable purification for photoresist use. Toprovide for appropriate temperature ranges, the fractional distillationcan be performed under significantly reduced pressures, and appropriatefractionation can be useful to reduce contaminants. In particular,initial fractions can be discarded and/or a portion of the compositioncan be left remaining in the initial distillation container. Thisfractionation can decrease higher boiling point and lower boiling pointcomponents with a modest reduction of yield while achieving a higherpurity of the product.

An example of a fractional distillation apparatus is shown schematicallyin FIG. 1.

Fractional distillation apparatus 100 comprises a distillation container102, such as a round bottom flask, a heating element 104, such as aheating mantle or oil bath, distillation column 106, pump 108, pressuretubing 110 connecting pump 108 to the distillation system to maintainthe system at a selected pressure, a pressure sensor 112 can be used tomonitor the pressure, temperature sensor 114, such as a thermometer canbe used to monitor the temperature in the distillation column, condenser116 can collect vapor coming off the distillation column 106, andcollection system 118 can collect purified liquid coming off of thecondenser. Collection system 118 can comprise a rotatable cow joint 122with three receiver connectors 124, 126, 128 that connect to threecollection flasks 130, 132, 134, such as Schlenk bomb flasks. Collectionflasks 130, 132, 134 can be rotated to position a selected flask forcollection. The rotatable cow joint 122 can further comprise valves. Theconfiguration can be adapted for a different number of collectionflasks, such as two, four or more. The volume of distillation container102 can be selected to be a suitable size for the amount of product tobe purified, and heating element 104 can be configured to efficientlyheat distillation container 102. Condenser 116 can be cooled withcirculating water or other coolant. Suitable components for fractionaldistillation apparatus 100 are available commercially.

To reduce the temperature of the distillation process, the pressure canbe reduced, for example, to a pressure from about 0.01 Torr to about 10Torr, in further embodiments from about 0.025 Torr to about 5 Torr, andin further embodiments from about 0.05 Torr to about 2.5 Torr. A personof ordinary skill in the art will recognize that additional ranges ofpressures within the explicit ranges above are contemplated and arewithin the present disclosure. A suitable fractional distillation columncan be used with a volume suitable for the process, and these arecommercially available. Fractional distillation columns include surfacesfor condensation and re-vaporization along the column. Thus, in someembodiments, a column can be, for example, filled with a suitable inertpacking material, such as Pro-Pak® distillation packing from Sigma(316SS), or it can be a Vigreux column with glass fingers extending intothe vapor space. The column may or may not be insulated, and the thermalgradient along the column can be adjusted by the length of the column,insulation of the column, and the ambient temperature.

The temperature can be controlled in the vessel holding the material tobe purified and along the column to achieve the desired separation. Thethermal conditions for one embodiment are presented in the Examplesbelow for both a monoalkyl tin triamide and a monoalkyl tin trialkoxide,and these conditions can be readily generalized for other compositionsbased on the teachings herein. For the distillation, the temperature ofthe heating bath can generally be set from about 50° C. to about 180° C.and in further embodiments from about 65° C. to about 150° C. A personor ordinary skill in the art will recognize that additional ranges oftemperature within the explicit ranges above are contemplated and arewithin the present disclosure. If the non-tin metal compositions and thepolyalkyl tin contaminants have a significantly higher or lower boilingpoint than the monoalkyl tin triamides or the monoalkyl tintrialkoxides, the other metals as well as the polyalkyl tin compositionscan be separated away during the distillation process to produce thepurified monoalkyl tin compositions. TREN or a similar tertadentatenon-planar chelating agent as noted above is added to the distillationflask to complex impurity species that otherwise co-distill with thedesired monoalkyl tin compositions. Moreover, fractions can be takenwith selected volumes of liquid removed in each fraction during stagesof the fractional distillation. The Examples demonstrate good separationwith reasonable yield free from detectable contaminants.

For particular removal of contaminants with lower boiling point, thesecontaminants can be separated away by collecting and discarding aninitial fraction during the distillation process. In some embodiments,the discarded initial fractions optionally can include at least theinitial 0.1 vol %, in further embodiments at least the initial 0.5 vol%, in other embodiments, at least the initial 1 vol % and in additionalembodiments from about 1 vol % to about 20 vol % can be discardedrelative to the initial volume charged into the distillation vessel. Inthe examples below, a highly purified product was obtained withoutdiscarding any initial fractions. In some sense, the keeping of afraction of the distillation material in the distillation flask has beenfound to be more significant for the purification process. Additionallyor alternatively, to remove higher boiling contaminants, a fraction ofthe initial composition can be left remaining in the distillationvessel. In some embodiments, the amount of composition left remaining inthe distillation vessel can be at least about 0.5 vol %, in furtherembodiments at least about 1 vol %, in other embodiments at least about3 vol %, and in additional embodiments from about 1 vol % to about 30vol % for purification of the monoalkyl tin triamides, and, forpurification of the monoalkyl tin trialkoxides, at least about 0.5 vol%, in further embodiments from about 0.75 vol % to about 12 vol %, andin other embodiments from about 1 vol % to 10 vol %. A person ofordinary skill in the art will recognize that additional ranges offractionation within the explicit ranges above are contemplated and arewithin the present disclosure.

In general, there may be a tradeoff of purity versus yield in theselection of the amount of initial collection fractions to discard andthe amount of initial composition to leave remaining the distillationvessel. Depending on the boiling point differences relative tocontaminants as well as the purity of the initial composition prior tofractional distillation, the addition of a tetradentate chelating agentand control of the fractional distillation process can assist withimproving yield within the constraints of the compositions. Of course,if contaminants copurify with the desired compositions due to closesimilarities of the boiling points, the fractional distillation may notachieve the desired purification. It has been found that desirablemonoalkyl tin triamides and, in particular, monoalkyl tin trialkoxidescan be produced with metal contaminants reduced to very low levels,which is presumed to be related to the relative boiling points of metalcontaminants and their complex formation with a tetradentate chelatingagent such as TREN.

Further processing of the purified monoalkyl tin compositions generallyinvolves dilution of the compositions with an organic solvent. Thediluted compositions can be used to carry out further reactions, such asthe reaction of the monoalkyl tin triamides to form monoalkyl tintrialkoxides, or to form a resist coating. The diluted compositions canbe filtered to remove particulates. The filtering can be performed atone or more suitable process points, such as prior to use in a furtherreaction, prior to placement of a resist composition into a containerfor storage and/or transport, and/or in a process line via delivery on acommercial wafer track. Improved processing is described herein, whichis especially useful for filtering monoalkyl tin trialkoxides.

If configured appropriately, a single filtration can in principleachieve desired low particulate levels. In some embodiments, thefiltering apparatus can be configured for performing repeated filteringof the organometallic composition, such as by configuring the system forrecirculation and/or for performing serial filtration. For recirculationof the filtered composition, the container can be fitted with a drainport and a return fill port. A pump or pumps can be used to drive theflow of fluid through the filtration system, and a suitable filter canbe used in line to remove small particulates from the fluid. Cleantubing can be used to connect the system with flow between therespective components.

A schematic layout of a filtration system 140 is shown in FIG. 2. Thecomposition to be filtered can be in a container 142 with an outlet 144,an inlet 146 and access port(s) 148. Flow from outlet can be controlledwith one or more pumps 150. The flow path then passes through a firstfilter 152 and optionally additional filter(s) 154. A flow meter 156 canbe used to monitor the flow rate through the system. A particle analyzer158 can be configured to measure particle within the filtered flow.While FIG. 2 shows particle analyzer 158 in line with the flow, othersuitable configurations can be used, such as a sampling configuration.Filtered flow can be directed for recirculation through recirculationline 160 connected to inlet 146 of container 142 or for collectionthrough collection line 162 directed to collection container 164. Avalve 165 can be used to selectively direct flow to either recirculationline 160 or collection line 162. In some embodiments, valve 166 can beused to divert filtered flow to collection container 168, such as in arecirculation configuration when the particle count drops below aselected value. Flow can be directed through suitable tubing, such aspolymer tubing.

Fluid in collection container 164 can be further filtered if desired ineither a recirculation configuration or another serial filteringconfiguration. A recirculation configuration for collection container164 can be conceived by conceptually reproducing the circular flow loopconnected to container 142 comprising pump(s), filter(s), particleanalyzer, and other desired components, with these componentsspecifically connected to collection container 164. As depicted in FIG.2, a second serial filtration configuration is shown. Flow from outlet170 of collection container 164 can be controlled with one or more pumps172 that direct flow to one or more filters 174. Flow from filter(s) 174can be directed past a particle analyzer 176 that can be in line or in asampling configuration, and a flow meter 178, positioned at a convenientlocation along the flow path. Filtered flow can be collected in bottle180. Again, suitable polymer tubing or other suitable flow conduits canbe used to direct the flow through the filtration system. Further serialfiltering and/or combinations with recirculation and serial filteringcan be performed if desired through a repeat of the filtration system.In a filtration system with two or more stages, the filters used for alater stage filtration can be selected to have a finer particle removalcapability. For example, a first stage filtration can be performed witha filter rated at a particle size cut off of 5 nm to 15 nm, and a secondstage filtration can be performed with a filter rated at a particle sizecut off of 1 nm to 3 nm. In some embodiments, the first stage filtrationcan involve recirculation, while a second stage is serial.

For embodiments in which the container is configured in a closed loopconfiguration to provide for the recirculation, a lid to the containerproviding the composition to be filtered can be configured with aplurality of ports. One port can be used for removal of the fluid to bepumped to the filter, another port can be used to deliver the filteredfluid back into the container, and other ports can be used for variousadditional functions. For example, another port of the container lid canbe used to deliver the filtered fluid to a packing container. A specificembodiment of a filtering apparatus is described in more detail in theExamples below.

While generally any one of a variety of pumps can be used to drive thefiltration flow, it has been discovered that impeller style pumpsprovide surprisingly improved filtration performance. While not wantingto be limited by theory, the more even pressures delivered by animpeller style pump are believed to improve the performance of thefilter for particulate removal by reducing pressure fluctuations. Theimproved filtering is confirmed in the Examples where filtering with animpeller style pump is contrasted with a diaphragm style pump using thesame filter. Suitable impeller style pumps include in particularmagnetic levitation impeller pumps from Levitronix® GmbH (Switzerland).Due to the high viscosity of the monoalkyl tin trialkoxides, two or moreLevitronix® pumps can be placed in series to obtain a desired flow rate.The magnetic levitation pumps provide low shear on the liquid duringpumping as well as a steady pressure. Flow rates through the systemgenerally depend on the filter selection, pump selection, tubing size,temperature, and pressure, which is influenced by the fluid viscosity.

Filters suitable for resist compositions based on in-line filtering arecommercially available. For example, photoresist filters are availablefrom Entegris (e.g., Impact® line of filters) and Nippon Pall Co. Ltd(Japan, e.g. PE-Kleen filters and PhotoKlean™ DDF P-Nylon). The ratedparticle filtration size of the filter can be specified down to >5 nm,but the smaller pore sizes can reduce the flow rate. As described in theExamples, desirable performance is obtained with a filter rated withpore sizes <10 nm. In general, the particle filtration rating can be 50nm (i.e., removing particles with sizes greater than 50 nm), 25 nm, 10nm, 5 nm, 3 nm, 2 nm, or 1 nm. A person of ordinary skill in the artwill recognize that additional ranges of particle filtration ratingswithin the explicit ranges above are contemplated and are within thepresent disclosure.

For particle removal, the purified monoalkyl tin composition afterfractional distillation can be placed in a clean container equipped forpumping out the composition for filtration. Suitable filtration systemsare summarized above. As noted above, various configurations can beused. For recirculation, the composition can be recirculated generallyfrom once to 100 times, and in further embodiments from 2 to 40 times.For serial filtration, the composition can be serially filtered once to10 times. A person of ordinary skill in the art will recognize thatadditional ranges of numbers of filtration steps within the explicitranges above are contemplated and are within the present disclosure. Thefiltration can be performed prior to placing the radiation resistcomposition into a container for shipping and/or in a production lineimmediately prior to use of the composition for patterning purposes. Inany case, the filtration system can be configured to avoid contaminationof the radiation resist composition with metal contaminants and/orparticulate contaminants. If the filtered compositions are placed incontainers for shipping, the containers can be sealed and appropriatelyshipped to end use facilities, at which appropriately clean processingcan be used for transfer of the compositions into process equipment.

EXAMPLES Example 1. Preparation and Purification of Alkoxide Precursorfrom Amide

This example demonstrates the synthesis and purification of monoalkyltin trialkoxides from a monoalkyl tin triamide precursor. The synthesisand purification of the triamide is demonstrated first.

Part A: Synthesis and Purification of t-BuSn(NMe₂)₃ Precursor

t-BuSn(NMe₂)₃ was prepared by reaction of t-BuMgCl and Sn(NMe₂)₄ indiethyl ether; t-BuMgCl (2.0 M) and Sn(NMe₂)₄ (99.9% trace metals basis)were supplied by Sigma Aldrich. In the reaction, the t-butyl group fromthe Grignard reagent substitutes for one dimethyl amide (—N(CH₃)₂)group. The ¹¹⁹Sn NMR spectrum in FIG. 3 shows the approximate molecularpurity of the product t-BuSn(NMe₂)₃ (δ=−85.6 ppm) to be 94%, asdetermined by peak integration; 1% is (t-Bu)₂Sn(NMe₂)₂ (δ=−56.2 ppm),and the remaining 5% is Sn(NMe₂)₄ (δ=−120.2 ppm).

In a glovebox filled with Ar(g) and <0.5 ppm O₂(g), 1202.57 g oft-BuSn(NMe₂)₃ were charged into a two-neck 2-L round bottom flask with a1.25-inch egg-shaped stir bar. A 34.3 g (6 mol %) quantity oftris(2-aminoethyl)amine (TREN, Alfa Aesar) was added to the flask andstirred, forming a milky white suspension. One neck of the 2-L flask wasequipped with a Teflon valve and the other sealed with a 24/40 glassstopper. The flask was removed from the glovebox and connected to aSchlenk line.

Purification was performed using the following packed columndistillation setup:

-   -   Heidolph Hei-Tec stir plate with Pt/1000 RTD probe and        temperature feedback control.    -   Silicone oil bath.    -   300-mm vacuum jacketed 24/40 Hempel style distillation column        (Sigma Aldrich)    -   0.24-in 316 stainless steel saddle mesh column packing        (Ace-Glass)    -   Vacuum jacketed 24/40 short-path distillation head with        water-cooled condenser. (Chemglass)    -   1-L Schlenk bomb as collection flask        The vacuum distillation was carried out using an oil bath        temperature between 115° C. and 120° C. and an absolute pressure        of approximately 500 mTorr, resulting in a distillate vapor        temperature in the range of 58-62° C. No initial distillate was        discarded and 872.6 g of purified t-BuSn(NMe₂)₃ was recovered,        resulting in a yield of 77.2%. At the end of the distillation        approximately 275 grams of material are retained in the        distillation flask and the packed column. It should be noted        that the presence of TREN effectively retains the unreacted        Sn(NMe₂)₄ and the (t-Bu)₂Sn(NMe₂)₂ impurity in the distillation        flask. The ¹¹⁹Sn NMR spectrum in FIG. 4, showing a single peak        at δ=−85.6 ppm, confirms isolation of a pure product.

To evaluate the non-tin metal contaminants of the distilledt-BuSn(NMe₂)₃, a sample of the triamide was diluted with 2-methyl2-butanol to a tin concentration of about 0.05M with respect to Snconcentration. The product was subjected to elemental analysis usingInductively Coupled Plasma-mass spectroscopy (ICP-MS) and/or InductivelyCoupled Plasma-atomic emission spectroscopy (ICP-AES) at ChemTrace (CA,USA). The measurements were performed in triplicate. The results for 23elements are presented in Table 1.

TABLE 1 Trace Metals Analytical Results Concentration in ppb DetectionLimits 1 2 3 1. Aluminum (Al) 0.7 1.5 2.0 1.1 2. Arsenic (As) 0.7 <0.7<0.7 <0.7 3. Barium (Ba) 0.5 0.87 <0.5 0.57 4. Cadmium (Cd) 0.5 <0.5<0.5 <0.5 5. Calcium (Ca) 0.7 3.4 3.3 4.6 6. Chromium (Cr) 0.5 <0.5 <0.5<0.5 7. Cobalt (Co) 0.5 <0.5 <0.5 <0.5 8. Copper (Cu) 0.7 1.2 1.1 1.1 9.Gold (Au) 0.7 <0.7 <0.7 <0.7 10. Iron (Fe) 0.7 <0.7 <0.7 <0.7 11. Lead(Pb) 0.7 <0.7 <0.7 <0.7 12. Lithium (Li) 0.5 1.5 1.1 3.4 13. Magnesium(Mg) 0.5 4.0 2.3 3.9 14. Manganese (Mn) 0.5 <0.5 <0.5 <0.5 15. Nickel(Ni) 0.7 <0.7 <0.7 <0.7 16. Palladium (Pd) 0.7 <0.7 <0.7 <0.7 17.Potassium (K) 0.7 <0.7 <0.7 <0.7 18. Silver (Ag) 0.7 <0.7 <0.7 <0.7 19.Sodium (Na) 0.7 9.4 5.7 22 20. Titanium (Ti) 2 <2 <2 <2 21. Tungsten (W)0.5 <0.5 <0.5 <0.5 22. Vanadium (V) 0.7 <0.7 <0.7 <0.7 23. Zinc (Zn) 0.75.9 6.9 6.8 Note: All elements were analyzed by ICP-MS/ICP-AES.

Part B: Conversion of t-BuSn(NMe₂)₃ to t-BuSn(OtAm)₃

In a glovebox filled with Ar(g) and <0.5 ppm O₂(g), the purifiedt-BuSn(NMe₂)₃ (2824 mmol) from Part A was charged into a two-neck 2-Lround bottom flask equipped with a 1.25-inch egg-shaped stir bar. 772 g(8755 mmol) of anhydrous 2-methyl-2-butanol (Sigma Aldrich, ≥99%) wereadded to a two-neck 1-L round bottom flask. One neck of the flask wassealed with a 24/40 rubber septum and a Teflon valve attached to theother. The flask was then removed from the glovebox and connected to aSchlenk line. The t-BuSn(NMe₂)₃ flask was cooled in an isopropylalcohol/dry ice bath (cryobath) before slowly adding the2-methyl-2-butanol (t-Amyl alcohol) using a stainless steel 16-gaugecannula and 1-2 psi of N₂(g) pressure. An 18-gauge needle was used as avent for the reaction flask to allow the generated dimethylamine gas toescape. Once the addition was complete, the reaction flask was removedfrom the cryobath and allowed to warm to room temperature under N₂(g).After warming to room temperature, the septum was replaced with a 24/40glass stopper and excess solvent was stripped under vacuum anddiscarded.

The product was then distilled under vacuum with a setup similar to thatdescribed in Part A, wherein a small 75-mm vacuum-jacketed Vigreuxcolumn replaced the large packed column. The distillation was carriedout using an oil bath temperature of 155° C. and an absolute pressurenear 500 mTorr, resulting in a distillate vapor temperature in the range104-108° C. A 1201.68 g quantity of product was recovered resulting in ayield of 97.3% for this step. No initial distillate material isdiscarded. At the end of the distillation, approximately 30 grams ofmaterial remains in the distillation flask. FIG. 5 shows the ¹¹⁹Sn NMRspectrum of the product. GC-MS analysis shows that it contains 0.28±0.1%(t-Bu)₂Sn(Ot-Am)₂ (δ=−114.2 ppm) as a molecular impurity.

Example 2: Photoresist Formulation

This Example demonstrates the composition and characterization of aphotoresist formulation.

A 1 M solution of t-BuSn(Ot-Am)₃ in 4-methyl-2-pentanol (>99.5% purity)was initially prepared. Approximately one mole (437.225 g) of thealkoxide precursor from Example 1 was weighed and transferred inside aglovebox to a 1 L volumetric flask; 4-methyl-2-pentanol was then addedto the flask. The solution was transferred to a fume hood, andadditional 4-methyl-2-pentanol was added to bring the total volume to 1L. The formulated resist was then transferred to a 1 L brown AicelloCorp. CLEANBARRIER™ (CB) bottle. The molarity was checked viacalcination to SnO₂, confirming a precursor concentration of 1.0 M. Theformulation was then diluted in a 20-L NowPak™ container to a finalvolume of 20 L and a final concentration of 0.044 M. Table 2 summarizesthe ICP analysis of this solution, performed by ChemTrace (Fremont,Calif., USA).

TABLE 2 ICP Analysis of Photoresist formulation. Trace Metals AnalyticalResults Concentration in ppb Detection Limits 1 2 3 1. Aluminum (Al) 0.7<0.7 <0.7 <0.7 2. Arsenic (As) 0.7 <0.7 <0.7 <0.7 3. Barium (Ba) 0.50.61 0.67 0.75 4. Cadmium (Cd) 0.5 <0.5 <0.5 <0.5 5. Calcium (Ca) 0.7<0.7 <0.7 <0.7 6. Chromium (Cr) 0.5 <0.5 <0.5 <0.5 7. Cobalt (Co) 0.5<0.5 <0.5 <0.5 8. Copper (Cu) 0.7 <0.7 <0.7 <0.7 9. Gold (Au) 0.7 <0.7<0.7 <0.7 10. Iron (Fe) 0.7 <0.7 <0.7 <0.7 11. Lead (Pb) 0.7 <0.7 <0.7<0.7 12. Lithium (Li) 0.5 <0.5 <0.5 <0.5 13. Magnesium (Mg) 0.5 <0.5<0.5 <0.5 14. Manganese (Mn) 0.5 <0.5 <0.5 <0.5 15. Nickel (Ni) 0.7 <0.7<0.7 <0.7 16. Palladium (Pd) 0.7 <0.7 <0.7 <0.7 17. Potassium (K) 0.7<0.7 <0.7 <0.7 18. Silver (Ag) 0.7 <0.7 <0.7 <0.7 19. Sodium (Na) 0.7<0.7 <0.7 <0.7 20. Titanium (Ti) 2 <2 <2 <2 21. Tungsten (W) 0.5 <0.5<0.5 <0.5 22. Vanadium (V) 0.7 <0.7 <0.7 <0.7 23. Zinc (Zn) 0.7 <0.7<0.7 <0.7 Note: All elements were analyzed by ICP-MS/ICP-AES.

In Table 2, the values marked with “<” symbols indicate that theconcentration for these metals was below the detection limit. Thus, forall of the metals examined, only Ba was above the detection limit, andfor this metal the measured values were below 1 ppb. It can reasonablybe assumed that for the other metals not directly measured that theirconcentrations will be comparable to the measured values in Table 2based on the relative natural abundances of the metals.

Example 3. Photoresist Formulation Particle Count

The following example demonstrates and compares the filtration of thephotoresist solutions to remove particulates with impeller and diaphragmstyle pumps.

Part A: Impeller pump.

Filtration of the alkoxide solution began immediately after dilution.The filtration system is shown schematically in FIG. 6. The mixing tanksystem 200 contains 5 connection ports at the top of the tank. Theseports allow for the following: filtration via recirculation (ports 202,204), tank cleaning via spray ball (port 206), argon injection (port208), and headspace pressure monitoring (port 210). The filtration loopconsists of two magnetic levitation impeller pumps 212, 214 in series, atemperature probe, a 5-nm Entegris U/HP filter 216, pressure transducersbefore 218 and after 220 the filter, and a particle counting manifold222. Suitable clean tubing connects the components.

The solution was recirculated for one day to achieve 17 volumetricturnovers through the filter. Particle counts were monitored duringfiltration with a RION KS-41B laser system, which includes a syringesampler (KZ-31W) and controller (KE-40B1). The system quantifiesparticle counts in select channel sizes via light scattering methods tosizes as small as 70 nm. The final, filtered material was bottled in alaminar flow hood into Aicello CB bottles.

Particle counts for the 70, 150, and 200 nm channels are 3.80, 0.24, and0.12 per mL, respectively. Table 4 summarizes counts at all channels.

TABLE 3 Channel Size 70 nm 80 nm 90 nm 100 nm 150 nm 200 nm 250 nm 300nm 400 nm 500 nm Particles/mL 3.8 1.44 0.92 0.68 0.24 0.12 0.08 0 0 0

The filtration using the impeller pump was very effective at removal ofparticulates down to small sizes. The filtration results were notablyimproved over the equivalent filtration using the diaphragm pump, asdescribed above using a comparable system except for the different pump.

Part B: Diaphragm Pump

Filtration of the monoalkyl tin trialkoxide solution from Example 2began immediately after dilution. For this comparative filtrationexample, a 20 L NowPak container was equipped with a recirculation cap,allowing the solution to be circulated through a filtration loop.

The filtration loop consists of an electric diaphragm pump (Cole-ParmerPTFE-Diaphragm pump, Model #7090-42), pressure gauge, 5-nm Entegris UHPfilter, particle counting manifold, and a three-way valve. The solutionwas recirculated for approximately two days to achieve 28 volumeturnovers. Particle monitoring was carried out during filtration with aRION KS-41B laser system, which includes a syringe sampler (KZ-31W) andcontroller (KE-40B1). The system quantifies particle counts in selectchannel sizes via light scattering methods to sizes as small as 70 nm.The final, filtered material was bottled in a laminar flow hood intoAicello CB bottles. Particle counts for the 70, 150, and 200 nm channelsare 34.2, 2.40, and 1.44 per mL, respectively. Table 3 summarizes countsat all channels, which represent the summary of particulate levelsbefore bottling.

TABLE 4 Channel Size 70 nm 80 nm 90 nm 100 nm 150 nm 200 nm 250 nm 300nm 400 nm 500 nm Particles/mL 34.24 13.32 9.8 7.36 2.40 1.44 0.76 0.520.36 0.28

Comparison of the data in Table 3 with that in Table 4 shows thatfiltration with the impeller pump was more effective than the diaphragmpump for removal of particles at all sizes measured.

The embodiments above are intended to be illustrative and not limiting.Additional embodiments are within the claims. In addition, although thepresent invention has been described with reference to particularembodiments, those skilled in the art will recognize that changes can bemade in form and detail without departing from the spirit and scope ofthe invention. Any incorporation by reference of documents above islimited such that no subject matter is incorporated that is contrary tothe explicit disclosure herein. To the extent that specific structures,compositions and/or processes are described herein with components,elements, ingredients or other partitions, it is to be understood thatthe disclosure herein covers the specific embodiments, embodimentscomprising the specific components, elements, ingredients, otherpartitions or combinations thereof as well as embodiments consistingessentially of such specific components, ingredients or other partitionsor combinations thereof that can include additional features that do notchange the fundamental nature of the subject matter, as suggested in thediscussion, unless otherwise specifically indicated.

What is claimed is:
 1. A composition comprising a solvent and monoalkyltin trialkoxide (RSn(OR′)₃) or monoalkyl tin triamide (RSn(NR′₂)₃) witha tin concentration from about 0.005M to about 0.5M and having no morethan about 40 particles per mL with a particle size of at least about 70nm.
 2. The composition of claim 1 wherein solvent comprises an alcoholor mixture of alcohols.
 3. The composition of claim 1 having a tinconcentration from about 0.01M to about 0.25M, having no more than about5 particles per mL with a particle size of at least about 100 nm asdetermined by light scattering.
 4. The composition of claim 1 comprisinga monoalkyl tin trialkoxide.
 5. The composition of claim 1 wherein R isa branched alkyl ligand represented by R¹R²R³C—, where R¹ and R² areindependently an alkyl group with 1-10 carbon atoms, and R³ is hydrogenor an alkyl group with 1-10 carbon atoms.
 6. The composition of claim 1wherein R comprises methyl (CH₃—), ethyl (CH₃CH₂—), isopropyl(CH₃CH₃HC—), t-butyl ((CH₃)₃C—), t-amyl (CH₃CH₂(CH₃)₂C—), sec-butyl(CH₃(CH₃CH₂)CH—), neopentyl (CH₃)₃CCH₂—), cyclohexyl, cyclopentyl,cyclobutyl, or cyclopropyl.
 7. The composition of claim 1 furthercomprising a monoalkyl tin trialkoxide (R₁Sn(OR″)₃) or a monoalkyl tintriamide (R₁Sn(NR′₂)₃) wherein R is different from R₁ and R′ is the sameor different from R″.
 8. The composition of claim 1 wherein R′ comprisesa methyl group, ethyl group, isopropyl group, t-butyl group, or t-amylgroup.
 9. The composition of claim 1 having no more than about 30particles with a particle size of at least about 70 nm as determined bylight scattering.
 10. The composition of claim 1 comprising a monoalkyltin trialkoxide, R comprising methyl (CH₃—), ethyl (CH₃CH₂—), isopropyl(CH₃CH₃HC—), t-butyl ((CH₃)₃C—), t-amyl (CH₃CH₂(CH₃)₂C—), sec-butyl(CH₃(CH₃CH₂)CH—), neopentyl (CH₃)₃CCH₂—), or a combination thereof, andR′ comprising a methyl group, ethyl group, isopropyl group, t-butylgroup or a combination thereof, wherein the solvent comprises an alcoholor mixture of alcohols, and the composition having no more than about 5particles per mL with a particle size of at least 100 nm as determinedby light scattering.
 11. A method for preparing a radiation sensitivecomposition comprising solvent and an organometallic compositionselected from the group consisting of monoalkyl tin trialkoxide,monoalkyl tin triamide, or a mixture thereof, the method comprising:flowing the composition using an impeller style pump through a filter toremove particulate contaminants to form a filtered composition having aconcentration of particles measured by light scattering with a size ofat least 70 nm is below 100 particles per mL.
 12. The method of claim 11wherein the organometallic composition has a tin concentration fromabout 0.005M to about 1M.
 13. The method of claim 11 wherein the solventcomprises an alcohol or mixture of alcohols.
 14. The method of claim 11wherein the flow is maintained with a plurality of inline impellerpumps.
 15. The method of claim 11 wherein the filter is a semiconductorgrade filter with a particle filtration rating of no more than 50 nm.16. The method of claim 11 wherein the flowing comprises refiltering thefiltered composition until the filtered composition has the indicatedconcentration of particles, as measured by light scattering.
 17. Themethod of claim 11 wherein a filtration apparatus performing the flowingand refiltering is configured to recirculate the composition from amixing container with an inlet and an outlet.
 18. The method of claim 17wherein the mixing container comprises a lid configured with an inletport and an outlet port, respectively, providing access to therecirculating composition.
 19. The method of claim 17 wherein thefiltered composition is collected in a clean container, and therefiltering comprises flowing the filtered composition through a filterto further remove particles from the filtered composition.
 20. Themethod of claim 17 wherein refiltering is repeated at least 3 timesbased on the filtration of a volume of composition provided.
 21. Themethod of claim 17 wherein the refiltering of the filtered compositiontakes place until a measured concentration of particles with a size ofat least 70 nm is below 40 particles per mL.
 22. The method of claim 17wherein the refiltering of the filtered composition takes place until ameasured concentration of particles with a size of at least 100 nm isbelow 5 particles per mL.